The invention relates to apparatus used in the manufacture of rubber hose and in particular to apparatus used to vulcanize such hose.
Current manufacture of rubber hose, particularly reinforced rubber hose, typically includes forming an unvulcanized elastomeric hose structure around a flexible, solid rubber mandrel and encasing the hose and mandrel within a pressure sheath or cover of lead or other suitable material in preparation for vulcanizaton or "cure". The sheath is considered necessary to maintain pressure against the hose outer surface preventing any defects which might otherwise develop during vulcanization. Spooled or otherwise supported lengths of sheathed, mandreled, unvulcanized hose are then placed in heated enclosures, such as ovens, where they remain until cured. After removal from the oven, the outer sheath is stripped and the internal mandrel removed from the vulcanized hose.
Proposed modified or alternate techniques in this field often involve improving hose vulcanization by obviating need for the normally necessary outer pressure sheath and/or effecting vulcanization or cure of hose in a more continuous manner. Exemplary of such proposals are the continuous passage of sheathed hose into a vulcanizing chamber, around a moving spool therein and withdrawal from the chamber (e.g. see U.S. Pat. No. 3,690,796); carrying of the hose through a tubular chamber by means of hot vulcanizing fluid such as oil (see U.S. Pat. Nos. 1,661,888 and 3,475,397); and moving the hose through long, heated, salt, or other particulate, bath-type troughs.
Principal advantages allegedly achieved by transport of hose through a tubular chamber by hot fluid are that the use of an outer pressure sheath over the hose during cure is unnecessary, that such a technique lends itself readily to space-saving designs, and that the procedure is continuous. However, it is often found that certain elastomeric hose, particularly of the reinforced type, vulcanized by such techniques delaminates or develops holes, blisters, and other serious functional and/or cosmetic defects, unless the hose transporting and vulcanizing fluid is sufficiently pressurized while circulating through the chamber. Furthermore, when using such techniques in vulcanizing mandreled hose, pressurization of the curing and transporting fluid is practically essential to maintain the inner diameter of the hose uniform.
However, to continuously transport hose through a tubular chamber with hot, pressurized fluid presents further problems in operation and safety which have prevented widespread use of what should theoretically be a more simplified and efficient approach to vulcanization of hose. Primary of these problems rest largely in the provision of adequate sealing which will dependably confine the hot, circulating, high pressure fluid within the curing chamber, but still permit entry and exit of the limp or flaccid hose in a simple, efficient, expeditious and continuous manner.